Historic Counties

There are thirteen historic counties of Wales (including Monmouthshire), the last of which were created by the Laws in Wales Act 1535. For the purposes of biological recording each historic county forms an eponymous vice county, with the detached parts of Flintshire treated as being in Denbighshire.

Boundary

The land-based border between Wales and England. This is well defined, but the lack of copyright-free data means that the OSM boundary has been derived from NPE data and its accuracy may be limited.

The maritime border between Wales and international waters. This was defined by the Government of Wales Act 2006, section 158: “Wales” includes the sea adjacent to Wales out as far as the seaward boundary of the territorial sea. The territorial boundary is in general 12 nautical miles (22.22 km) from the mean low water mark. In OSM, this has been automatically derived from coastline data.

The maritime border between Wales and England, extending from land along the Dee and Severn estuaries to the territorial limit. This remains poorly defined and has been arbitrarily mapped as following a line roughly equidistant between the English and Welsh mean low water marks.

The boundary for Wales' maritime unitary authorities is generally at the 3 mile limit except where special provisions apply where islands are within three miles of more than one Unitary authority or where unitary authorities are themselves closer than 3 miles to one another. Thus the division between Anglesey and Gwynedd is a notional line down the Menai Strait. For Gwynedd the boundary includes Bardsey island and out to a limit of 3 miles beyond.